Technical Field
The present invention relates to a copolymer, ink and an ink container.
Background Art
Inkjet recording methods have advantages such that the process is simple and full colorization is easy in comparison with other recording methods. Therefore, high resolution images can be obtained by a device having a simple configuration. For this reason, the inkjet recording is widely diffusing from home use to office use, commercial printing, and industrial printing. In such an inkjet recording method, aqueous ink compositions using a water soluble dye as colorant are commonly used. However, its water resistance and light resistance are inferior so that pigment ink using a water insoluble pigment is under development to substitute the water soluble dye.
For inkjet ink printing for office use, recording media, typically plain paper, are used and high image density is demanded. In general, when images are printed on plain paper using pigment ink, the pigment ink does not stay on the surface of the paper but permeates into the paper, so that the pigment density on the surface decreases and consequently the image density lowers. The image density increases if the pigment concentration in the ink is increased. However, the ink becomes viscous, thereby degrading the discharging stability of the ink.
In addition, technologies to stably form clear and vivid images with higher resolutions in higher performance are demanded in the fields of commercial printing and industrial printing. As the recording medium, in addition to plain paper, coated paper, art paper, non-permeating film such as polyethylene terephthalate (PET) film, etc. are used and high responsiveness of ink to such recording media is also demanded. In the inkjet recording method, a hydrophilic organic solvent is added to an aqueous ink to prevent curling of plain paper or to increase drying speed and prevent beading by improving the permeability of ink in the case of coated paper or art paper.
In addition, unlike an aqueous dye ink adjusted by dissolving a dye in water, the aqueous pigment ink for use in the inkjet recording method described above or pens and pencils requires stable dispersion of an water-insoluble pigment in water for a long period of time. Therefore, various pigment dispersants have been developed.